If i have two 3D sketches made without exiting the sketch
I activate the loft feature and I select a first profile as a close loop
Than I select a second profile also as a closed loop
In the preview I can see a part formed
We click OK and a part is formed.
If I edit this loft feature,
in the property manager there is a drag sketch button.
Click on it and with the cursor you can dynamically change the sketch. Like this
Or like this.
Click OK and you have your part changed.